Polycystic kidney disease (PKD) is the most common inherited renal disease, accounting for 5-10% of end-stag renal disease with an annual cost of $240,000,000. The etiology of renal cysts is especially important for the children an adults with inherited PKD who may require dialysis or transplantation for survival. We have a newly describe transgenic mouse model of PKD, called inv/inv, which will be used to conduct studies not possible in humans. The long term goal of this project is to understand how the inheritance of a novel situs inversus gene, inv, results in PKD and loss of renal function. Our general strategy is to study the kidneys of inv/inv mice, which share phenotypic features with autosomal recessive (AR) PKD. They develop situs inversus, PKD and die prematurely from renal failure. The inv gene has been fully cloned and sequenced. Our preliminary data suggest inv is an intracellular protein with discrete localization in specific segments of the nephron. Our experiments will test the hypothesis that the inv gene codes for a developmentally important protein that maintains nephron integrity. Grant funding is a major factor in the PI's immediate goal of attaining research independence and the long-term career goal of becoming a successful and productive investigator in an academic institution. The specific aims of this present study are as follows: 1. To characterize the inv/inv mouse model of ARPKD, we will perform single and dual photon fluorescence microscopy with cell-specific antibodies and lectins. Immunogold electron microscopy with anti-inv antibodies will target the intracellular localization of the inv protein. These microscopy experiments will allow us to appropriately direct mechanistic studies of inv protein function and interactions. 2. In situ hybridization studies will be used to determine the cellular levels of inv messenger RNA during critical periods of development. This is especially important, as incremental variations in mRNA expression are known to occur during narrow developmental windows. 3. We will use green fluorescent protein-inv constructs and anti-inv antibodies t establish spatial and temporal inv expression patterns during development. We believe the inv/inv model offers a new an exciting opportunity to extend the understanding of the genetic mechanisms of nephrogenesis and the abnormalities in this process which lead to PKD.